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Biomedical subjects

B J Potter

Publications and source records attributed to B J Potter.

At least 37 records · Page 2Linked to original sources
PubMed1996

Digital enhancement of radiographs: can it improve caries diagnosis?

Unlike traditional radiographs, digital images are electronically alterable and offer the potential for enhancing diagnostic information. The authors conducted a small-scale study to examine differences in clinicians' diagnoses of caries using traditional radiographs and digitized images vs. microscopic diagnosis. Two general dentists and one oral-maxillofacial radiologist scored the images for caries. This study suggests that digital enhancements may aid some clinicians in caries diagnosis.

Dental Caries↗
PubMed1996

Spatial resolution and angular alignment tolerance in radiometric analysis of alveolar bone change.

This pilot study was undertaken to determine the effect of x-ray beam alignment and spatial resolution on quantification of alveolar bone using radiometric techniques. Six (6) dry mandibles were radiographed at 70 kVp, 10 mA, 0.6 seconds using D-speed film, with a bone chip (2.64, 4.10, or 6.07 mg) present or absent at 7 x-ray beam alignments (0 degree, 2 degrees horizontal, 2 degrees vertical, 4 degrees horizontal, 4 degrees vertical, 6 degrees horizontal, 6 degrees vertical). This resulted in 28 radiographs per mandible. Radiographs were digitized using 50- and 200-microns pixel spatial resolution. Image gray levels were standardized using a simple look-up table shift. Regions of interest (ROIs) were positioned on the alveolar bone where the bone chips had been placed. Cumulative percent histograms (CPH) were calculated for those ROIs. Regression analysis was used to evaluate the relationships between CPH changes and bone chip size as x-ray beam angulation and spatial resolution was varied. The resulting R2 values for angulation ranges of 0 degree to 1.4 degrees, 1.5 degrees, to 2.4 degrees, and 2.5 degrees to 5.5 degrees were: 0.983, 0.941, 0.891 for 50-microns pixel images and 0.869, 0.909, and 0.774 for 200-microns pixel images. We conclude that 50-microns pixel spatial resolution is apparently superior to 200-microns pixel images if radiometric data is to be evaluated. With 50-microns pixel spatial resolution, alignment variations up to 5 degrees may be acceptable in clinical studies, depending on the magnitude of bone change that is to be detected.

Alveolar Process↗
PubMed1995

Reproducibility of beam alignment using different bite-wing radiographic techniques.

Longitudinal radiographic assessment of crestal alveolar bone plays an important role in the diagnosis and long-term evaluation of periodontal disease in patients. Because practitioners use several radiographic techniques to obtain bite-wing radiographs, horizontal and vertical alignment errors could adversely affect the diagnostic impression gained from this type of radiographic examination. The objective of this study was to determine the alignment reproducibility of three different clinical techniques used to acquire bite-wing radiographs. Patients who require bite-wing radiographs as part of a dental school screening process were radiographed with modified standard bite-wing tabs and two different intraoral positioning devices. Horizontal and vertical angular deviations were measured and alignment errors were calculated for each radiograph. The mean total angular alignment error for the standard bite-wing tab technique was 6.2 degrees, whereas the mean alignment error for both positioning devices was less than 1.8 degrees. The results of this study suggest that an intraoral positioning device for acquiring bite-wing radiographs should be used.

Alveolar Bone Loss↗
PubMed1995

Intrafilm controls to standardize grey level variations in digitized radiographs.

OBJECTIVES: Radiometric analysis can be used to identify small changes in grey levels taken from investigator-defined regions of interest (ROIs). To do this, standardization of the radiographic optical densities and image grey scales is considered essential. Rigid standardization is one of the impediments to applying existing radiometric techniques to clinical practice. The purpose of this study was to evaluate the use of grey-level variations from a series of intrafilm control regions of interest (ROIs) to adjust radiometric grey-level data taken from test ROIs. METHODS: After digitization, ROIs were drawn on three locations: the background, anatomical crown, and tooth root. Mean grey levels, histograms and cumulative percent histograms (CPHs) were determined for each group. With the goal of decreasing the distribution of these curves from their unadjusted grey-level positions to zero (superimposing all curves), shifts required to align the control CPHs were applied to test CPHs. Changes between the pre- and post-adjusted CPH distributions were measured. RESULTS: Intrafilm controls provided a combined decrease of 45.3% in the grey-level distribution error. CONCLUSION: While CPHs can be adjusted using intrafilm controls, these adjustments may have limited benefit.

Humans↗
PubMed1994

Isolation and immunolocalization of a rat renal cortical membrane urate transporter.

Two modalities of urate transport have been reported in rat kidney, a urate/anion exchanger and a potential sensitive, uricase-like uniporter. As an initial attempt to isolate and characterize the responsible transport protein(s), rat renal cortical membranes were harvested, solubilized, and subjected to affinity chromatography with urate or xanthine as the affinity ligand. Pig liver peroxisomal uricase was purified with the same system, and the enzymatically active protein was used to generate polyclonal antibodies in rabbit. Silver stain of SDS-polyacrylamide gel electrophoresis gels of the eluted fraction containing the affinity-purified renal membrane protein(s) demonstrated bands at 25, 32, 36, and 41 kDa. On Western blot, two of these bands (32 and 36 kDa) were immunoreactive to the polyclonal antibody to pig liver uricase. In 6 of 10 studies, the affinity-purified renal membrane protein(s) also oxidized urate. Anti-pig liver uricase produced a selective and dose-dependent inhibition of the uricase-like urate uniporter in renal membrane vesicles, but did not affect the urate/anion exchanger or the sodium-dependent glucose transporter. Immunocytochemical studies of rat renal cortex with the same antibody indicated that the immunoreactivity was localized to proximal tubules. These studies demonstrate that the renal cortical plasma membranes contain urate-binding proteins, which have some functional and immunological homology to the hepatic peroxisomal core protein, uricase. Within the renal cortex, these proteins are localized to proximal tubules, the site of urate transport. Since the antibody that reacts with the affinity-purified urate-binding proteins on Western blot selectively inhibits urate transport in intact membrane vesicles, it is concluded that at least one of the affinity-purified urate-binding proteins is a uricase-like urate transporter.

Animals↗
PubMed1994

Induction of a dose-related increase in sulfobromophthalein uptake velocity in freshly isolated rat hepatocytes by phenobarbital.

To determine whether phenobarbital affects hepatocellular bilirubin/sulfobromophthalein uptake mechanism, we administered it to male Sprague-Dawley rats, body weight 175 +/- 25 gm, at doses of 1 to 75 mg/kg body wt/day for 7 days. Control rats were given an equivalent volume of physiological saline solution. On day 8, hepatocytes were isolated by means of collagenase perfusion, suspended in Hanks' solution without albumin and incubated with high specific activity (3 Ci/mmol) [35S]sulfobromophthalein, which was synthesized in our laboratory and purified by means of a new reverse-phase high-pressure liquid chromatography procedure. The initial uptake rate of sulfobromophthalein was determined at sulfobromophthalein concentrations of 1 to 50 mumol/L with a rapid filtration technique. The maximum uptake velocity and Michaelis constant for sulfobromophthalein uptake at each phenobarbital dose were determined by means of a computer analysis. In control studies, maximum uptake and Michaelis constant were 48.0 +/- 16.7 (mean +/- S.D.) pmol/50,000 cells/min and 22 +/- 4 mumol/L, respectively. Maximum uptake velocity increased linearly with the log of the phenobarbital dose (r = 0.98, p < 0.01), the increase achieving statistical significance at a dose of 3 mg/kg/day. Michaelis constant, however, was essentially unchanged at phenobarbital doses of 50 mg/kg/day or less. The maximal observed increase in maximum uptake velocity of sulfobromophthalein (to 619% of control values) was appreciably greater than the maximal increase in UDP-glucuronyltransferase activity (200% of control) or immunoreactive ligandin concentrations (260% of control) seen in earlier studies, suggesting a direct effect on the plasma membrane transport mechanism.

Animals↗
PubMed1994

von Willebrand factor binding to collagen in patients with end-stage renal disease.

Bleeding abnormalities are common in patients with end-stage renal disease (ESRD). Although von Willebrand factor (vWF) abnormalities have been suspected in patients with ESRD, none have been clearly defined. Because vWF function is related to its collagen-binding capacity, we investigated whether this parameter might be altered in patients with ESRD. We measured vWF binding to type III collagen and levels of vWF antigen and ristocetin cofactor in 20 patients undergoing hemodialysis before and after routine hemodialysis sessions, in 10 patients with ESRD who had not previously undergone dialysis, and in 22 healthy, nonsmoking persons who served as controls. We found significant increases of vWF antigen levels in all patients with ESRD (undialyzed: mean, 6.4 +/- 3.0 U/ml, p < 0.001; before dialysis: mean, 5.1 +/- 4.0 U/ml, p < 0.001; after dialysis: mean, 4.8 +/- 3.4 U/ml, versus 0.81 +/- 0.26 U/ml in controls, p < 0.001). The ristocetin cofactor levels were increased in the patients who had not undergone dialysis (mean, 1.30 +/- 1.26 U/ml, p = 0.04), whereas both before and after hemodialysis groups (means, 0.71 U/ml and 0.75 U/ml, respectively) were not significantly different from controls (mean, 0.72 +/- 0.30 U/ml, p = 0.96 and p = 0.8, respectively). Patients with ESRD who had not undergone dialysis showed no difference in vWF binding to collagen (mean, 1.21 +/- 0.63 U/ml) compared with the control group (mean, 1.16 +/- 0.13).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

35-mm film scanner as an intraoral dental radiograph digitizer. I: A quantitative evaluation.

A 35-mm slide scanner digital imaging system was tested for its suitability in digitizing intraoral dental radiographic film for quantitative studies. The system (Nikon model LS-3510AF Nikon Electronic Imaging, Nikon, Inc., Melville, N.Y.) uses a charge-coupled device linear photodiode array. The data content in the original film images was evaluated, and the system performance assessed objectively with the use of specially designed test films. Radiometric and geometric performances for the digitizing system were extracted from measurements and observations, and these were compared with published data for two other film digitizing systems (video camera DAGE MTI, Michigan City, Ind. and Barneyscan 35-mm film digitizer Barneyscan, Berkeley, Calif.). The techniques used to evaluate this system are easy and suitable for evaluation of any digitizing system. This scanner system (Nikon) was superior to previously evaluated systems in transforming and recording radiographic film densities across the range (0.3 to 2.0 optical density units) of clinically relevant optical densities. The scanner offers substantial advantage over the other digitizing systems for gray scale information from clinically important optical densities.

Evaluation Studies as Topic↗
PubMed1993

35-mm film scanner as an intraoral dental radiograph digitizer. II: Effects of brightness and contrast adjustments.

Typical 35-mm slide scanners use a photodiode array and software that allows for digital and analog controls that are manually adjustable. The digital controls provide brightness and contrast adjustments, whereas corresponding analog controls adjust the exposure time and black level that determines the clamping level of the charge-coupled device for the maximum black in the image. The objective of this study was to determine the effects of these controls on the radiometric data of intraoral dental radiograph images, to establish recommended settings, and to set specific standard guidelines for the digitization process. Three approaches were used. The results of this study demonstrate that brightness and contrast control alterations on the digitizer produces different optical densities and modulation transfer function values. The impact of these results is unresolved yet must be considered in analysis on quantitative radiometric studies.

Evaluation Studies as Topic↗
PubMed1993

Central giant cell granuloma. Report of a case.

The central giant cell granuloma is a tumor that has great potential for the displacement of teeth and the development of a facial deformity. Although its cause and behavior are still matters for discussion, its early diagnosis and treatment are a priority. We describe a patient with a large benign central giant cell granuloma of the anterior mandible. The clinical, radiographic, and histologic appearance, as well as the appropriate treatment, are discussed in light of the current literature.

Adolescent↗
PubMed1993

Utilization of radiographs for a state dental board examination.

A survey of 97 dentists who had recently taken a state dental board examination was completed to document the use of radiographs for the screening and treatment of their patients. The response rate was 53%. Candidates spent on average 14.25 hours screening a mean of 18 patients to identify the dental pathoses necessary to take the examination. Candidates took a mean of 28.9 (+/- 25.8) radiographs for screening purposes and during the examination with a range of 3 radiographs to a maximum of 141 radiographs. Time in practice and specialty status did not affect the total number of radiographic exposures made. The majority of radiographs taken (53%) were unlikely to be used in the direct care of the patient's dental needs. The results of this survey indicated that efforts to minimize administrative radiographs should be increased.

Adult↗
PubMed1993

Effect of chronic alcohol feeding on hepatic iron status and ferritin uptake by rat hepatocytes.

Alcohol abuse is known to cause disturbances to iron homeostasis in man and is associated with elevated serum ferritin levels. We have previously shown that ethanol metabolism in the rat hepatocyte is associated with an immediate reduction in ferritin uptake by this cell. In this study we have examined the effect of pair-feeding the Lieber-DeCarli liquid alcohol diet on ferritin uptake by rat hepatocytes. Rat liver ferritin was radiolabeled with 59Fe in vivo and isolated by conventional techniques. Rats were pair-fed the Lieber-DeCarli liquid alcoholic diet for 4-6 weeks. Hepatocytes, isolated from their livers by collagenase perfusion, were incubated with [59Fe]ferritin in L-15 medium at 37 degrees C and 4 degrees to measure ferritin uptake and binding. The in vitro effect of ethanol on these hepatocytes was also studied. Ferritin and iron parameters were measured in the sera and hepatocytes of these animals and a comparable group of normal chow-fed rats. The rate of ferritin uptake by hepatocytes from alcohol-fed rats was significantly faster than that of their pair-fed controls (0.743 +/- 0.061 vs. 0.540 +/- 0.042 ng/min/10(6) cells, p < 0.05). However, the rats on Lieber-DeCarli control diet exhibited a lower hepatocyte ferritin uptake rate than chow-fed animals (79.3 +/- 8.1% of the control values, p < 0.01). In vitro incubation of cells in 100 mM ethanol resulted in less inhibition of ferritin uptake by hepatocytes from alcoholic rats than from their pair-fed controls (11 +/- 7.1% inhibition vs. 43.6 +/- 10.7% for controls, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde↗
PubMed1993

Co-localization of von Willebrand factor and type VI collagen in human vascular subendothelium.

The binding of von Willebrand factor (vWF) to subendothelium constitutes an important initial step in the process of platelet adhesion to exposed subendothelium following blood vessel injury. We previously demonstrated that vWF is present in human vascular subendothelium and recently found that a 150 kd vWF-binding protein, which we extracted from subendothelium, is type VI collagen. Although we have established that vWF and type VI collagen bind in vitro, it is not known whether these two proteins are associated in the vascular subendothelium in situ. We, therefore, 1) investigated the morphological effects of our biochemical extraction procedure on human umbilical veins by scanning and transmission electron microscopy, 2) analyzed the subendothelial extract by immunofluorescence for the presence of vWF and collagens and by electron microscopy for morphological characteristics, and 3) localized vWF and type VI collagen in subendothelium by immunofluorescence and by single- and double-label immunoelectron microscopic studies with protein A-conjugated gold particles. We found that the surface exposed following de-endothelialization is composed of microfibrils and contains very little fibrillar collagen. The subendothelium is stripped after sodium dodecyl sulfate-urea extraction, and the extract itself contains immunoreactive vWF and type VI collagen but no immunoreactive type I or III fibrillar collagens. Immunofluorescence and immunoelectron microscopic studies showed that vWF and type VI collagen are both present in subendothelium, where both co-localized to microfibrils. In conclusion, vWF that binds to type VI collagen in vitro, also co-localizes with type VI collagen in subendothelium, where both are associated with microfibrils. Type VI collagen, therefore appears to serve as a biologically significant binding site for vWF in vivo and may thereby play a role in mediating platelet adhesion to exposed subendothelium following vascular injury.

Collagen↗
PubMed1992

Adipocyte differentiation of 3T3-L1 cells involves augmented expression of a 43-kDa plasma membrane fatty acid-binding protein.

A previously described 43-kDa plasma membrane fatty acid-binding protein (FABPPM) was not observed by immunohistochemical methods in proliferating 3T3-L1 fibroblasts. However, it was detectable in plasma membranes by the second day of confluent growth, prior to accumulation of visible lipid droplets, and was strongly expressed in 8-day differentiated adipocytes. These observations were confirmed by extraction of plasma membrane proteins and subsequent immunoblotting. Kinetics of initial [3H]oleate uptake by both fibroblasts and adipocytes consisted of the sum of a saturable and a non-saturable component. During differentiation the saturable component increased progressively. Vmax increased from 3 to 25 to 110 pmol.s-1.mg cell protein-1 between the fibroblast, the 4-day, and 8 day adipocyte stages; Km was 24 nM in fibroblasts and approximately 55 nM in both 4- and 8-day differentiated adipocytes. By contrast, the rate constant for nonsaturable oleate influx decreased progressively from 0.026 to 0.010 ml.s-1.mg protein-1 between the fibroblast and 8 day adipocyte stages. In 8-day adipocytes saturable oleate uptake was inhibited by up to 55% by antibodies against rat liver FABPPM; these antibodies had no effect on uptake of 2-deoxyglucose or the medium chain fatty acid octanoate. They also had no effect on oleate uptake by fibroblasts. These studies support the hypothesis that FABPPM is a component of a saturable transport mechanism for long chain fatty acids.

3T3 Cells↗
PubMed1992

Iron uptake from transferrin and asialotransferrin by hepatocytes from chronically alcohol-fed rats.

Chronic alcohol intake is often associated with alterations to iron homeostasis and an increase in the serum levels of carbohydrate-deficient transferrin. As the liver is a major iron storage site and also synthesizes transferrin, the normal serum iron transport protein, the aim of this study was to test the hypothesis that these disturbances in iron homeostasis were caused by altered hepatocyte iron uptake from the abnormal transferrin. To achieve this, we have investigated iron uptake from both transferrin and asialotransferrin by hepatocytes from male Sprague-Dawley rats fed the De Carli and Lieber alcohol diet. Iron uptake from transferrin by hepatocytes from alcoholic rats was less than 60% that of control values, and in the presence of 50 mM ethanol decreased still further to 35% of the uptake by the corresponding control cells. Iron uptake from rat asialotransferrin was reduced in both groups when compared to that observed from normal transferrin; 13% by control cells and 39% by hepatocytes from alcohol-fed rats. Alcohol, however, had no further effect on asialotransferrin uptake by either hepatocytes from alcohol-fed rats, or their pair-fed controls. Transferrin binding to hepatocytes was also influenced by the alcohol diet. Although there was no difference in binding at 37 degrees C, cells from alcohol-fed rats bound 85% of this total at 4 degrees C, compared to 44% by control hepatocytes. Similar values were also obtained for hepatocyte binding of asialotransferrin; alcohol feeding resulted in an increase in binding at 4 degrees C to 73% from 58% with control cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcoholism↗
PubMed1992

The effect of ethanol metabolism on ferritin uptake by freshly isolated rat hepatocytes: is acetaldehyde responsible for this alteration?

Alcohol abuse is associated with disturbances to iron metabolism in man, ranging from anemia to siderosis. Also seen in these patients are increased serum ferritin levels. Since the liver not only stores iron in cytosolic ferritin, but has also been shown to take up this molecule from the plasma by an active transport mechanism, it has been suggested that the iron in this circulating ferritin may contribute to the increased incidence of siderosis seen in alcoholics. As part of an ongoing study of these disturbances, using a rat model, we have examined the uptake of ferritin by freshly isolated hepatocyte suspension to test the hypothesis that increased hepatocyte uptake of ferritin iron contributes to the siderosis seen in some alcoholics. Incubation of hepatocytes in the presence of ethanol resulted in a progressive reduction in uptake with increasing alcohol concentration, from 1.23 +/- 0.05 ng of ferritin/10(6) cells/min to 0.65 +/- 0.02 ng/10(6) cells/min (mean +/- SD) at an ethanol concentration of 100 mM. 4-Methylpyrazole (0.1 mM) restored 70% of this activity, but higher concentrations also decreased ferritin uptake in the absence of ethanol. The addition of 5 microM cyanamide decreased ferritin uptake slightly in the presence of ethanol (0.82 +/- 0.04 ng of ferritin/10(6) hepatocytes/min vs. 0.86 +/- 0.03 ng/10(6) cells/min for ethanol alone), while having no effect in the absence of ethanol (1.01 +/- 0.04 vs. 1.12 +/- 0.05 ng/10(6) cells/min). Preincubation of the hepatocytes with acetaldehyde resulted in a dose-dependent reduction to a maximum reduction of approximately 25% at 300 microM acetaldehyde.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde↗